I agree more or less with Trash. Conservative buyers could get an SE and plug in a 17"+ monochrome monitor. The graphics card provided tear off menus, so the DTP operator could assemble a palette of tools on the SE built-in display with the work on the big monitor. The advantage of using a big monitor on a compact Mac was that the operator could disconnect the display and carry the SE off to the typesetter.
The SE/30 took this a stage further, so the external monitor could be greyscale or colour. There was no need for the built-in monitor to be greyscale because it was primarily intended for palettes, desk accessories etc.
DTP was not the only industry that used this work process. Compact Mac plus big monitor was a popular configuration for scientists and engineers.